Our Night Sky: October 2021

We had the Autumnal Equinox at the end of last month and with it comes ever shorter days and longer nights, making it ideal for stargazing. Although there are not too many bright stars in the lower half of the sky, there is much to see higher up, with the Great Square of Pegasus entering our southern night sky. There’s also a chance of seeing some shooting stars, with the peak of the Draconids Meteor Shower on the night of 8/9 October and the peak of the Orionids meteor shower on the night of 21/22 October.

Under the Plough I - Sanna Bay, Sanna, Ardnamurchan
Looking north over Sanna Bay on a starry night to the Small Isles of Muck, Eigg and Rum, with the 7 bright stars of Ursa Major (the Plough) visible to the left of the sky.

The Constellations

​This month, the sun sets around 6:30 pm and the stars and the constellations start to become visible from about 8:00 pm onwards. Even though we are now into Autumn, the Summer Triangle, which is made up of the three bright stars of Vega, Altair and Deneb, is still visible and can be used to navigate your way around the night sky. Start off by finding Vega, a really bright white star which will be high up in the sky to the South-West. Just face south, look up, then look right and you will find it. Next is Altair, which you will find below Vega, halfway down towards the horizon and slightly to the left. Finally, there is Deneb, which will be almost directly above Altair and above and to the left of Vega.

The Milky Way, which has dominated the night sky over the last couple of months can still be seen during the early part of the night. Just trace a line down from Deneb, through Altair and you should be able to make out its band of stars as it flows down to the horizon, with the last of its cloudy core visible and to the right of Saturn and Jupiter as they sit just above the horizon.

​At the moment there are not many bright stars in the lower part of the southern sky, so if you are in an area with light-pollution, look higher up and you should be able to pick out some constellations. Below Vega, you will see the 4 other main stars that make up the constellation of Lyra (the Lyre). These form a small parallelogram and make up the body of the Lyre – the sky’s only musical instrument.

Next, look at Deneb, which marks the top of the Northern Cross, or the constellation of Cygnus (the Swan), and flies down the Milky Way with its wings outstretched. Deneb marks the tail of the Swan and Albireo, a fairly faint star at the bottom of the constellation, marks its head. If you have a telescope, or even powerful binoculars, take a look at Albireo and you’ll see that it’s a double star of contrasting colours. Typically, people see them as yellow and blue, or more accurately yellowish and bluish.

The Constellation of Pegasus
Image Credit: Till Credner
Own work: AlltheSky.com, CC BY-SA 3.0

​Finally, looking at Altair, you will find the constellation of Aquila (the Eagle) because Altair is its brightest star. Altair also has outstretched wings, though they are not as obvious at the wings of Cygnus. In between these two flying birds is the constellation of Sagitta (the Arrow), a dim but distinctive shape which is reasonably easy to pick out. Another small but easily seen constellation called Delphinus (the Dolphin) is nearby and it also looks like what it’s meant to be. 

Southern Night Sky - October 2021
Created using SkyPortal Mobile App

Northern Night Sky - October 2021
Created using SkyPortal Mobile App

​If you look high up and slightly to the South-East, you’ll find the Square of Pegasus a large asterism made up of 4 stars of nearly equal brightness in a large square pattern. These are Scheat, Alpheratz, Markab and Algenib. The constellation of Pegasus represents the Flying Horse of Greek mythology and the Square marks the horse’s body. You may find it difficult to make out the horse because it is upside down and the constellation represents only the top half of its body and its head. However, you may be able to pick out Enif, the constellation’s brightest star which will be about halfway between the bottom right of the Square and Altair. Enif is an orange supergiant star that is 5,000 times brighter than the Sun and it represents the horse’s nose.
 
If you look north, you’ll see the same stars as you would in any other month, but their orientation varies from month to month. In October the familiar Plough asterism, which many people will recognise, is moving from the north-west to the north. Follow its two right-hand stars upward, veer a little bit to the right and you’ll find Polaris, the Pole Star. If you look over to the north-east you can see Capella. It is a yellow giant star, the brightest star in the constellation of Auriga (the Charioteer), the sixth-brightest star in the night sky, and the third-brightest in the northern celestial hemisphere after Arcturus and Vega.

The Moon

At the very start of the month, we just miss the last quarter Moon as it was on 29 September, while there is a new Moon (no Moon) on 6 October. So, if it’s clear on the evening of 9 October, you will find the slightest of crescent Moons setting in the west at around 7:00 pm with a bright Venus below and to the left it.

The first quarter Moon (a half moon) is on 13 October and on 14 October it will be sitting beneath Saturn and Jupiter, about half way in between these two gas giants, while on 15 September, it will have moved to the left of Jupiter.

This month’s full Moon is called the Hunter’s Moon because traditionally, people in the Northern Hemisphere spent the month of October preparing for the coming winter by hunting, slaughtering and preserving meats for use as food. Like the last month’s Harvest Moon, the Hunter's Moon is also particularly bright and long in the sky, giving hunters the opportunity to stalk prey at night.

This month’s full Moon is on the night of 20-21 October, becoming 100% full just before 4 pm on the afternoon of 21 October and then rising in the east a few hours later at just before 7:00 pm. It will be below and to the right of the Pleiades (The Seven Sisters) on 22 October and almost directly above Aldebaran, the red eye of Taurus the Bull, on 23 October. The last quarter Moon (a half moon) is on 28 October, rising in the north east, next to Praesepe (the Beehive Cluster) shortly after 11:00 pm.

​The Planets

When it is getting dark, you may be able to spot Venus hanging low down on the western horizon just before it sets at around 7:30 pm, or 6:30pm after the clocks change. It is gradually getting brighter because it is moving closer to Earth. On 29 October it reaches Elongation and is at its furthest from the Sun.
 
Saturn and Jupiter, two of our Solar System’s gas giants, are still visible above the southern horizon and Jupiter, the bigger and brighter of the two, will probably be the first thing you see when it’s getting dark. Saturn will appear to its right about half an hour after you first see Jupiter. They will travel just above the southern horizon until they set, with Saturn doing this first at around midnight and Jupiter following at around 2:00 am.
 
Neptune will be above the horizon until about 4:30 am and you will find it to the left of Jupiter in Aquarius. However, it will be very dim and therefore difficult to see, even with binoculars or a telescope. Its near twin in size, Uranus, can be found further over to the east in Aries, rising at about 6:30pm and staying above the horizon all night. It will be just visible to the naked eye, although you’ll have a better chance of seeing it if you use binoculars or a telescope.
 
This is the best month of the year to see Mercury because it reaches its Elongation, or maximum separation from the Sun, on 25 October. If you look east at around 6:30 am that day, you may be able to see it, but because it keeps close the horizon, the best chance of success will be found if you are at an elevated position overlooking an open horizon with no trees and buildings to prevent you from seeing it.
 
Mars is too close to the Sun to be visible this month.

Meteor Showers 

​The Orionid meteors fly each year between about October 2 to November 7 and are caused by debris from Halley’s Comet smashing into the Earth’s atmosphere. You can spot them from the start of the month, but you can see the greatest number at meteor shower’s peak on the night of 21/22 October.
 
In a good year, you can expect to see about 10- 20 meteors/hour at the peak, but this year a near full moon will block out all but the brightest ones. However, if you do decide to look for them, wait until after 10:00 pm because that’s when their radiant point (the area of the sky where the meteors seem to originate) is to the top left of Orion as it rises in the east.
 
When watching for the meteors, give yourself at least an hour of observing time, because they will come in spurts, interspersed with lulls. Also remember that your eyes can take as long as 20 minutes to adapt to the darkness of night, so don’t rush the process. If you are patient, you may see some of the brightest Orionid meteors despite the Moon’s glare.
 
Alternatively, you could watch for the Draconid meteors at nightfall and early evening on October 8 as there will be little or no moon to drown them out. You might catch some on the two nights either side of that as well. You’ll find the radiant point for the Draconid meteor shower a little bit to the right of Vega and right next to the head of the constellation Draco the Dragon.
 
The Draconid shower is a real oddity, in that the radiant point stands highest in the sky as darkness falls. That means that unlike many meteor showers, more Draconids are likely to fly in the evening hours than in the morning hours after midnight. Also, this shower is known as “a Sleeper” because in most years it produces only a handful of meteors per hour. However, do look out for them because the Draconids’ unpredictable nature, as seen in both 1933 and 1946, means that you could enjoy thousands of meteors in only one hour.